1. Field of the Invention
The present invention relates to a solid electrolytic capacitor and, more specifically, to a solid electrolytic capacitor having a capacitor element mounted on a prescribed lead frame and sealed with mold resin portion.
2. Description of the Background Art
A solid electrolytic capacitor is one of electronic components that can be surface-mounted on a printed circuit board or the like. As shown in FIG. 41 or 42, a solid electrolytic capacitor 101 of this type includes a capacitor element 102, an anode lead frame 110, a cathode lead frame 120 and a mold resin portion 140 sealing these components. Capacitor element 102 has a substantially columnar (rectangular parallelepiped) anode body 103, an anode portion 104 protruded from the body, and a cathode portion 105 formed on an outer surface surrounding anode body 103. Anode lead frame 110 is electrically connected to anode portion 104 with a pillow member 180 interposed, and cathode lead frame 120 is electrically connected directly to cathode portion 105. Other than the pillow member, a member of different shape, formed to have a prescribed shape, is also used in some capacitors.
Solid electrolytic capacitor 101 of this type is manufactured in the following manner. First, a lead frame is punched out to have a prescribed shape, whereby a portion to be the anode lead frame and a portion to be the cathode lead frame are formed. Next, a conductive pillow member is welded on the portion to be the anode lead frame. Next, the anode portion of capacitor element is placed at a prescribed position with respect to the welded pillow member, and the cathode portion is placed at a prescribed position on the portion to be the cathode lead frame, and the capacitor element is attached to the lead frame.
Next, the portion to be the anode lead frame, the portion to be the cathode lead frame and the capacitor element are surrounded by a prescribed metal mold, and mold resin is poured to the metal mold, so that the capacitor element and the like are sealed. Thereafter, the mold resin portion sealing the capacitor element and the like is cut out at a prescribed position from the lead frame, and the solid electrolytic capacitor is completed. In the solid electrolytic capacitor, a part of anode lead frame and a part of cathode lead frame protrude as terminals, from the mold resin portion.
A method of welding the pillow member at the anode portion of capacitor element has also been proposed, rather than welding the pillow member at the portion to be the anode lead frame. The solid electrolytic capacitors of this type are disclosed, for example, in Japanese Patent Laying-Open Nos. 2006-319113 and 2002-367862.
The conventional solid electrolytic capacitor 101, however, has the following problems. As described above, in order to electrically connect anode portion 104 and anode lead frame 110 of capacitor element 102, pillow member 108 is positioned between anode portion 104 and anode lead frame 110. Therefore, when attaching capacitor element 102 to the lead frame, an additional member is required, and a process step of welding the pillow member 108 as such to the lead frame is additionally required, hindering reduction of manufacturing cost.
Further, when pillow member 180 is welded on anode portion 104 of capacitor element 102, location or strength of welding may vary, making it difficult to attach capacitor element 102 to the lead frame with high accuracy. This leads to lower production yield of solid electrolytic capacitor 101. Further, contact area between anode portion 104 and pillow member 180 is limited and, therefore, there is a limit in reducing equivalent series resistance of capacitor element 102.